scholarly journals Numerical Study of Lymph Mechanics

2021 ◽  
Author(s):  
◽  
Daniel J. Watson
Keyword(s):  
Lymphatic System ◽  
Numerical Study ◽  
Patient Specific ◽  
Single Subject ◽  
3D Analysis ◽  
Large Network ◽  
Lumped Model ◽  
Biphasic Model ◽  
Lymphatic Valve ◽  
Scale Modelling

Methods taken from engineering and computer science were applied to the lymphatic system. Starting with a 3D analysis of a single subject-specific lymphatic valve. A mechanism was presented to explain previous experimental results showing the effect of trans-mural pressure on the pressure required to close lymphatic valves. The impor-tance of wall motion in future FSI studies of lymphatic valve dynamics were identified. Previous approaches to lumped modelling of the lymphatic system were considered and modifications were proposed. A less-idealised valve model, incorporating trans-mural dependent bias, was proposed as well as a method of allowing self-organised contrac-tion through a stretch-dependent frequency of contraction. A network of the superficial lymphatics of the upper-limb was reconstructed from an anatomical sketch. The net-work was used in conjunction with the lumped model to produce a 421 vessel lymphatic model consisting of 17,706 lymphangions. Several issues which impede large network scale modelling of the lymphatic system are identified. A simplified patient-specific biphasic model of lymphoedema was proposed and used to develop a novel shape-based metric for lymphoedema. A statistically significant relationship between the metric and the presence of lymphoedema was found.

scholarly journals Variation of the Three-Dimensional Femoral J-Curve in the Native Knee

2021 ◽  
Vol 11 (7) ◽  
pp. 592
Author(s):  
Sonja A. G. A. Grothues ◽  
Klaus Radermacher
Keyword(s):  
Geometric Parameter ◽  
Knee Kinematics ◽  
Size Variation ◽  
Principal Component ◽  
Parameter Analysis ◽  
Patient Specific ◽  
3D Analysis ◽  
Relative Location ◽  
Shape Variation ◽  
J Curve

The native femoral J-Curve is known to be a relevant determinant of knee biomechanics. Similarly, after total knee arthroplasty, the J-Curve of the femoral implant component is reported to have a high impact on knee kinematics. The shape of the native femoral J-Curve has previously been analyzed in 2D, however, the knee motion is not planar. In this study, we investigated the J-Curve in 3D by principal component analysis (PCA) and the resulting mean shapes and modes by geometric parameter analysis. Surface models of 90 cadaveric femora were available, 56 male, 32 female and two without respective information. After the translation to a bone-specific coordinate system, relevant contours of the femoral condyles were derived using virtual rotating cutting planes. For each derived contour, an extremum search was performed. The extremum points were used to define the 3D J-Curve of each condyle. Afterwards a PCA and a geometric parameter analysis were performed on the medial and lateral 3D J-Curves. The normalized measures of the mean shapes and the aspects of shape variation of the male and female 3D J-Curves were found to be similar. When considering both female and male J-Curves in a combined analysis, the first mode of the PCA primarily consisted of changes in size, highlighting size differences between female and male femora. Apart from changes in size, variation regarding aspect ratio, arc lengths, orientation, circularity, as well as regarding relative location of the 3D J-Curves was found. The results of this study are in agreement with those of previous 2D analyses on shape and shape variation of the femoral J-Curves. The presented 3D analysis highlights new aspects of shape variability, e.g., regarding curvature and relative location in the transversal plane. Finally, the analysis presented may support the design of (patient-specific) femoral implant components for TKA.

Numerical study on the hemodynamics of patient-specific carotid bifurcation using a new mesh approach

2018 ◽  
Vol 34 (6) ◽  
pp. e2972 ◽  
Author(s):  
S.I.S. Pinto ◽  
J.B.L.M. Campos ◽  
E. Azevedo ◽  
C.F. Castro ◽  
L.C. Sousa
Keyword(s):  
Numerical Study ◽  
Carotid Bifurcation ◽  
Patient Specific

Numerical Study on Mechanical Behavior of Tissue-Engineering Repaired Cartilage in Sliding Load Condition

2013 ◽  
Vol 441 ◽  
pp. 598-601
Author(s):  
Yu Zhou ◽  
Hai Ying Liu ◽  
Yu Tao Men ◽  
Li Lan Gao ◽  
Bao Shan Xu ◽  
...  
Keyword(s):  
Numerical Study ◽  
Compressive Strain ◽  
Load Condition ◽  
Repair Process ◽  
Cartilage Defects ◽  
Biphasic Model ◽  
Artificial Cartilage ◽  
Repairing Effect ◽  
Intensity Of Exercise ◽  
Engineered Cartilage

Mechanical state has a major impact on the repairing effect of tissue-engineered cartilage. The unusual state could result in the degeneration of artificial and host cartilage. A repaired cartilage defects was simulated by finite element simulation based on fiber-reinforced biphasic model in sliding load condition. The results showed that in the surrounding area of defects Mises stress, compressive strain and pore pressure are affected by the amount of compression and modulus of materials. Inadequate modulus leads to the declining mechanical bearing ability in defected position, while excessive modulus leads to increasing difference between the pressure on the two sides of bonding surface between artificial cartilage and host cartilage. During the repair process, it is suggested to choose the artificial cartilage modulus with both reasonable bearing ability and less stress concentration should be considered, and the intensity of exercise should also decrease to reduce the amount of compression.

scholarly journals Numerical Investigation of the Characteristics of the In-Cylinder Air Flow in a Compression-Ignition Engine for the Application of Emulsified Biofuels

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1517
Author(s):  
Mohd Fadzli Hamid ◽  
Mohamad Yusof Idroas ◽  
Mazlan Mohamed ◽  
Shukriwani Sa'ad ◽  
Teoh Yew Heng ◽  
...  
Keyword(s):  
Fuel Injection ◽  
Numerical Study ◽  
Guide Vane ◽  
Engine Performance ◽  
3D Analysis ◽  
Compression Ignition Engine ◽  
Ansys Fluent ◽  
Start Of Injection ◽  
Crank Angle ◽  
Start Of Combustion

This paper presents a numerical analysis of the application of emulsified biofuel (EB) to diesel engines. The study performs a numerical study of three different guide vane designs (GVD) that are incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. The GVD variables were used in three GVD models with different vane heights, that is, 0.2, 0.4 and 0.6 times the radius of the intake runner (R) and these were named 0.20R, 0.40R and 0.60R. The SCC piston and GVD model were designed using SolidWorks 2017, while ANSYS Fluent version 15 was used to perform cold flow engine 3D analysis. The results of the numerical study showed that 0.60R is the optimum guide vane height, as the turbulence kinetic energy (TKE), swirl ratio (Rs), tumble ratio (RT) and cross tumble ratio (RCT) in the fuel injection region improved from the crank angle before the start of injection (SOI) and start of combustion (SOC). This is essential to break up the heavier-fuel molecules of EB so that they mix with the surrounding air, which eventually improves the engine performance.

scholarly journals Individually Tailored Treatment Targeting Motor Behavior, Cognition, and Disability: 2 Experimental Single-Case Studies of Patients With Recurrent and Persistent Musculoskeletal Pain in Primary Health Care

2005 ◽  
Vol 85 (10) ◽  
pp. 1061-1077 ◽  
Author(s):  
Pernilla Åsenlöf ◽  
Eva Denison ◽  
Per Lindberg
Keyword(s):  
Health Care ◽  
Primary Health Care ◽  
Pain Intensity ◽  
Musculoskeletal Pain ◽  
Pain Control ◽  
Motor Behavior ◽  
Patient Specific ◽  
Single Subject ◽  
Primary Health

Abstract Background and Purpose. This article introduces an individually tailored intervention targeting motor behavior, cognition, and disability in patients managed by physical therapists in primary health care. Effects on self-rated disability, pain intensity, and pain control are described. Subjects. Two women with recurrent or persistent disabling musculoskeletal pain were selected. Methods. Two experimental single-subject A1-B-C-A2 studies with multiple baselines across situations were used. Principal outcome data were collected daily with patient-specific continuous measures for 3 weeks before intervention, continuously during intervention, and for 2 weeks during each of the 1-, 4-, 6-, and 12-month follow-up examinations. Results. Disability and pain intensity decreased, and pain control increased in both subjects. The results were maintained at the follow-up examinations. Discussion and Conclusion. Positive outcomes of the intervention were reported from 2 subjects with recurrent and persistent disabling pain. Procedures for systematic tailoring of treatment to behavioral goals and individual patient characteristics are available as a result of the successful application. The results need to be replicated in future clinical controlled group studies.

scholarly journals Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity

2017 ◽  
Author(s):  
Ali Farnoud ◽  
Xinguang Cui ◽  
Ingo Baumann ◽  
Eva Gutheil
Keyword(s):  
Nasal Cavity ◽  
High Performance ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Patient Specific ◽  
Process Time ◽  
Nasal Valve ◽  
Time Step ◽  
Real Process

The present numerical study concerns the dispersion and deposition of a nasal spray in a patient-specific human nose. The realistic three-dimensional geometry of the nasal cavity is reconstructed from computer tomography (CT) scans. Identification of the region of interest, removal of artifacts, segmentation, generation of the .STL file and the triangulated surface grid are performed using the software packages ImageJ, meshLab, and NeuRA2. An unstructured computational volume grid with approximately 15 million tetrahedral grid cells is generated using the software Ansys ICEM-CFD 11.0. An unsteady Eulerian-Lagrangian formulation is used to describe the airflow and the spray dispersion and deposition in the realistic human nasal airway using two-way coupling. A new solver called pimpleParcelFoam is developed, which combines the lagrangianParcel libraries with the pimpleFoam solver within the software package OpenFOAM 3.0.0. A large eddy simulation (LES) with the dynamic sub-grid scale (SGS) model is performed to study the spray in both a steady and a pulsating airflow with an inflow rate of 7.5 L/min (or maximum value in case of the pulsating spray) and a frequency of 45 Hz for pulsation as used in commercial inhalation devices. 10,000 mono-disperse particles with the diameters of 2.4 µm and 10 µm are uniformly injected at the nostrils. In order to fulfil the stability conditions for the numerical solution, a constant time-step of 10−5 s is implemented. The simulations are performed for a real process time of 1 s, since after the first second of the process, all particles have escaped through the pharynx or they are deposited at the surface of the nasal cavity. The numerical computations are performed on the high-performance computer bwForCluster MLS&WISO Production using 256 processors, which take around 32 and 75 hours for steady and pulsating flow simulation, respectively. The study shows that the airflow velocity reaches its maximum values in the nasal valve, in parts of the septum and in the nasopharynx. A complex airflow is observed in the vestibule and in the nasopharynx region, which may directly affect the dispersion and deposition pattern of the spray. The results reveal that the spray tends to deposit in the nasal valve, the septum and in the nasopharynx due to the change in the direction of the airflow in these regions. Moreover, it is found that due to the pulsating airflow, the aerosols are more dispersed and penetrate deeper into the posterior regions and the meatuses where the connections to the sinuses reside.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4628

scholarly journals Micro scale jet impingement cooling and its efficacy on turbine vanes : a numerical study

2021 ◽  
Author(s):  
Santhiya Jayaraman
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Leading Edge ◽  
Jet Impingement ◽  
3D Analysis ◽  
Transfer Rates ◽  
Impingement Cooling ◽  
Micro Scale ◽  
Turbine Vane ◽  
Nozzle Configuration

A numerical analysis of effectiveness of micro-jet impingement cooling on leading edge of a turbine vane is presented. An axisymmetric single round jet was assessed for its ability and consistency as a preliminary study including the investigation of parameters influencing the heat transfer distribution. The analysis revealed that an increase in Nusselt number was attributed to increase in Reynolds number, decrease in jet diameter and H/D < 3. Significant improvement in heat transfer was observed for tapering nozzle configuration. The study was then further expanded to 3D analysis of leading edge cooling of turbine vane. Effect of nozzle diameter to micro-scale was studied, which showed 65% enhancement in the heat transfer rates.

Numerical Study of Depressurization Rate during Blowdown Based on Lumped Model Analysis

1984 ◽  
Vol 21 (12) ◽  
pp. 931-941 ◽  
Author(s):  
Takashi IKEDA ◽  
Atsuo YAMANOUCHI ◽  
Isao SUMIDA
Keyword(s):  
Numerical Study ◽  
Model Analysis ◽  
Lumped Model

scholarly journals Computational Analysis of Self-Expanding and Balloon-Expandable Transcatheter Heart Valves

Biomechanics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 43-52
Author(s):  
Salvatore Pasta ◽  
Caterina Gandolfo
Keyword(s):  
Aortic Valve ◽  
Heart Valves ◽  
Numerical Study ◽  
Flow Analysis ◽  
Patient Specific ◽  
Area At Risk ◽  
Virtual Planning ◽  
Local Maxima ◽  
Transcatheter Aortic Valve ◽  
Transcatheter Heart Valve

Bicuspid aortic valve (BAV) patients are usually excluded from transcatheter aortic valve implantation (TAVI) as this valve anatomy likely leads to oval expansion. This study presents a numerical study of TAVI using both self-expanding and balloon expandable transcatheter heart valve (THV) in bicuspid patients with severe stenosis. The simulation framework included a patient-specific anatomy of the aortic root, calcifications and BAV leaflets extracted from medical imaging analysis as well as a realistic crimping and deployment of the THV. Tissue stress analysis highlighted local maxima in the contact area between the inner aortic lumen and the THV stent frame. Flow analysis based on the smoothed particle hydrodynamics (SPH) technique displayed the area at risk of paravalvular leakage (PVL). These findings provide insights on the TAVI in BAV and thus represents a further step towards the use of in-silico for the virtual planning of TAVI, aiming at improving not only the efficacy of the implantation but also the exploration of borderline anatomy as the case of TAVI in BAVs.

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